1. Field of the Invention
The present invention relates to a ventilation waterproof connector and more specifically to a waterproof connector provided with a ventilation tube for introducing an outside air into the connector housing to prevent water permeation into the housing due to pressure difference between inside and outside of the housing.
2. Description of the Prior Art
When an ordinary waterproof connector having no ventilation tube is used under severe ambient conditions where temperature and/or pressure changes violently and therefore the connector packing is damaged, water readily enters into the connector housing from the outside due to pressure difference between the inside and the outside of the connector housing. To solve this problem, a ventilation tube is connected to the connector housing to match the connector inside pressure with the connector outside pressure. The reason why the ventilation tube is connected to the housing without simply forming a vent hole in the connector housing is to lead the free end of the ventilation tube to a safe place from which water will not be introduced into the connector housing.
A ventilation waterproof connector incorporated in an oil pressure switch for automotive vehicles will be described hereinbelow by way of example. This switch is turned on or off by a diaphragm housed in a pressure switch housing and moved by pressure introduced to one side of the diaphragm. Therefore, it is necessary to keep the other side of the diaphragm at a constant atmospheric pressure. In this case, when a vent hole is simply formed in the switch housing, there exists a problem in that water may enter into the switch housing and therefore the diaphragm may be corroded. Therefore, a ventilation tube is connected to the switch housing usually in parallel to the switch cable led to the pressure switch, in order to avert a complicated wire and tube arrangement.
As described above, in a waterproof connector used under severe ambient conditions or connected to a special device (e.g. pressure switches), an additional ventilation tube is connected in parallel to the connector cable in order to keep the inside pressure at a constant atmospheric pressure.
FIG. 1 is an example of prior-art ventilation waterproof connectors, disclosed in Japanese Published Examined (Kokoku) Utility Model Appl. No. 56-31030, entitled Breathing Tube for Waterproof Connector. In the drawing, a male connector housing 1 having two male connector terminals 3 is mated with a female connector housing 2 having two female connector terminals 4. Two wires 5 are inserted into two holes formed in the male connector housing 1, and retained to the housing 1 by wire stoppers 8. Each wire conductor 5a of the wire 5 is fixed to a conductor connecting portion 3a of the male connector terminal 3. In the same way, each wire conductor 9a of the wire 9 is fixed to a conductor connecting portion 4a of the female connector terminal 4. In addition, a ventilation tube 6 arranged substantially in parallel to the wires 5 and bundled by a tape is also inserted into a hole formed in the male connector housing 1 and retained to the housing 1 with a tube stopper 7.
In the prior-art ventilation waterproof connector shown in FIG. 1, since an additional ventilation stopper 7 to be designed for each connector housing 1 must be mounted to prevent the ventilation tube 6 from being removed from the male connector housing 1, there exists a problem in that the number of parts increases and different jigs must be prepared, thus resulting in a higher cost. Further, in the above-mentioned prior-art document (No. 56-31030), although a ventilation waterproof connector having no tube stopper is disclosed, since the free end of the ventilation tube is not retained firmly, there exists another problem in that the ventilation tube is not stably connected to the connector housing.
The above-mentioned drawbacks involved in the prior-art ventilation waterproof connector are not desirable, in particular when the connectors are assembled by an automatic assembly process or system.